BAf'TERIOLOGirAL EXAMIXATIOX. 205 



80° C. (176' F.) for twenty minutes. Incubate at 40' for forty- 

 eight hours ; if B. sporogen.es enteritidis is present, the milk is 

 curdled, and the dry-looking curd is nearly blown out of the tube. 



Interpretatimi of Results. — The presence of B. coli communis in 

 1 c.c. or less of the water, especially if accompanied by the presence 

 of B. sporogenes enteritidis, is a very unfavourable sign, and points 

 to sewage contamination. B. coli communis in 10 c.c. is very 

 suspicious, whilst if this organism is present in 100 c.c, but not 

 in less water, an investigation of the supply should be under- 

 taken, but the water should not be condemned on this ground 

 alone. 



The presence of glucose fermenting organisms which do not 

 prove to be B. coli communis is not a very favourable sign, but 

 the other evidence should be carefully considered before con- 

 demning ; they are often present in surface waters. 



The colonies liquefying gelatine aie usually those of putre- 

 factive organisms, and any great proportion is undesirable. The 

 immber of organisms growing on gelatine varies ^^leatly with 

 the source of the water. Water from deep wells should be 

 almost sterile and certainly should not give more than 100 colonies 

 per c.e. ; any number exceeding this may l)e taken as indicating 

 contamination with surface water. Surface wateis which are 

 not contaminated may contain man}- more (H'nanisnis. as many 

 as 2,000 per c.c, and often a large number of these (2") pci cent.) 

 liquefy gelatine; such waters are i;eiieially found to contain 

 organic matter derived from decayini: leaves and other vei;etable 

 matter. 



All waters giviiijj; evidence of organisms of intestinal origin, 

 and a immbcr of organisms running into many thousands on 

 gelatine, may be condemned as unsatisfactory. 



By the combined information from inspection of the source, 

 chemical analysis and bacteriological examination, a usually 

 reliable opinion can be made of the purity of the water: it is 

 even more reliable, if the data an:" compared with those obtained 

 on waters of known purity from the same district and of the 

 same character. 



For other methods of baeteiiological examination and for the 

 .separation and identification of individual species, works on 

 bacteriology must be consulted. 



Summary of Sanitary Precautions. — The foUowing recom- 

 mendations were made by a commission held under the auspices 

 of the British Medical ■/mininl : — 



1. That all milkinj; be carried on in the open air. the animals 

 and operators standing on a material which is capable of being 

 thoroughly washed, such as a floor of concrete or cement. Such 

 a floor could be easily laid down in any convenient place which 



